Do you really want to be put in the position of... I can't afford all the work to get my dog back to normal, so I'll have it put down.
We're got dog insurance for both our dogs. One dog has £6,000 a year spent on her, if she didnt, she would've been put down well over 8 years ago.
I know my vet very well and when an animal comes in that needs work.. They see it like this...
vet: has this animal got insurance?
vet: right, let's do x-rays, blood work, some more blood work, blah blah blah
If you don't have insurance it goes like this:
vet: got insurance?
vet: oh, we'll do an x-ray and see what that turns up, then we might need to do some blood. (this all takes longer, poor animal)
Basically if its insured, they throw the book at it, use the best drugs, get all tests done and so on. If its not, its a trade off between what the dog needs and what the owners can afford. Usually this results in longer treatment, and a lot of the time, the animal is put down.. after all they dont wanna pay £12-£30 per month on insurance, they sure as hell don't want to spend the £700 to get the animal back to normal.
Our youngest dog, had a little problem, and the bill came to well over £1000, thank god we only paid the excess of £50-£100.
BTW: You may struggle getting insurance for an older dog these days, also they will not cover it for anything it has had before... Say you went to the vets about an eye infection or something.. It will not be covered for that.. Get it done ASAP.